Generally a clutch device has friction plates (clutch plates or clutches) for transmitting a torque from a power source to a drive wheel by a frictional force and an actuator for driving the friction plates. For example, when the clutch plates in such a clutch device are worn (e.g. reduced in thickness), there is a possibility that the same frictional force cannot be obtained with the same driving amount by the actuator. Such a problem can be solved by detecting the amount of movement of the clutch plates from their separate position to their contact position and increasing the driving amount by the actuator according to an increase in the amount of movement of the clutch plates.
Japanese Patent Application No. 2004-197842 generally discusses a configuration that detects the amount of movement of the clutch plates according to a position of a member displaced by an actuator. Even though the timing of engagement of the clutch can be detected by the technique described in Japanese Patent Application No. 2004-197842, there is a possibility that a clutch control amount at starting of rotation of the drive wheel may be varied due to variations in quality of the clutch in manufacturing or an increase in friction in a driving force transmitting system. For example, when a larger clutch control amount is required to start the rotation of the drive wheel, it may be desirable that the clutch control amount can be suitably corrected so as to eliminate the above variations to make a vehicle operation feel more stable in such a manner that the operator does not feel a delay in response at starting.